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                <h2 class="post-title">
                    C3P0数据库连接池技术
                </h2>
                <div class="post-info">
                    <time class="post-time gt-c-content-color-first">
                        · 2021-01-02 ·
                    </time>
                    
                        <a href="https://zydnc.gitee.io/5RyDY5oFU/" class="post-tags">
                            # C3P0
                        </a>
                    
                        <a href="https://zydnc.gitee.io/java/" class="post-tags">
                            # Java
                        </a>
                    
                        <a href="https://zydnc.gitee.io/mysql/" class="post-tags">
                            # MySQL
                        </a>
                    
                </div>
                <div class="post-content">
                    <blockquote>
<p>本教程仅限于 <code>c3p0v0.9.5.2</code> + <code>mysql8.0</code> + <code>jdk1.8</code></p>
</blockquote>
<h2 id="一-在pomxml中加入c3p0依赖文件">一、在pom.xml中加入C3P0依赖文件</h2>
<p><code>如果是普通项目，需要解决依赖问题，c3p0的jar包依赖于mchange-common的jar包</code></p>
<pre><code class="language-xml">&lt;!-- https://mvnrepository.com/artifact/com.mchange/c3p0 --&gt;
&lt;dependency&gt;
    &lt;groupId&gt;com.mchange&lt;/groupId&gt;
    &lt;artifactId&gt;c3p0&lt;/artifactId&gt;
    &lt;version&gt;0.9.5.2&lt;/version&gt;
&lt;/dependency&gt;
</code></pre>
<h2 id="二-书写配置文件">二、书写配置文件</h2>
<h3 id="1-严格按照规定命名为-c3p0properties-文件">1. 严格按照规定命名为 <code>c3p0.properties</code> 文件</h3>
<p><code>这里需要注意和通常的不一样的是需要在每个key前加c3p0</code></p>
<pre><code class="language-properties">c3p0.driverClass=com.mysql.cj.jdbc.Driver
c3p0.jdbcUrl=jdbc:mysql://localhost:3306/数据库名?useUnicode=true&amp;characterEncoding=utf8&amp;serverTimeZone=UTC
c3p0.user=root
c3p0.password=123456
c3p0.initialPoolSize=10
c3p0.maxPoolSize=100
c3p0.checkoutTimeout=3000
</code></pre>
<h3 id="2-严格按照规定命名为-c3p0-configxml-文件">2. 严格按照规定命名为 <code>c3p0-config.xml</code> 文件</h3>
<p><code>这里需要注意一个地方就是jdbcUrl里本来用来连接各个参数的&amp;符号在xml文件中会被转义就如同html规则一般，所以我们想要使用表示&amp;符号的转义字符&amp;amp;来替换&amp;符号</code></p>
<pre><code class="language-xml">&lt;?xml version=&quot;1.0&quot; encoding=&quot;UTF-8&quot;&gt;
&lt;c3p0-config&gt;
    &lt;default-config&gt;
        &lt;property name=&quot;driverClass&quot;&gt;&lt;/property&gt;
        &lt;property name=&quot;jdbcUrl&quot;&gt;jdbc:mysql://localhost:3306/数据库名?useUnicode=true&amp;amp;characterEncoding=utf8&amp;amp;serverTimeZone=UTC&lt;/property&gt;
        &lt;property name=&quot;user&quot;&gt;root&lt;/property&gt;
        &lt;property name=&quot;password&quot;&gt;123456&lt;/property&gt;
        &lt;property name=&quot;initialPoolSize&quot;&gt;10&lt;/property&gt;
        &lt;property name=&quot;maxPoolSize&quot;&gt;100&lt;/property&gt;
        &lt;property name=&quot;checkoutTimeout&quot;&gt;3000&lt;/property&gt;
    &lt;/default-config&gt;
&lt;/c3p0-config&gt;
</code></pre>
<blockquote>
<p>本教程以Idea工具为例，所以如果是普通Java项目，请将配置文件置于src目录下，若是Maven管理的项目，请直接将配置文件置于resources目录下，具体原因详见JDBC篇</p>
</blockquote>
<h2 id="三-书写代码测试正常的数据连接对象的获取">三、书写代码，测试正常的数据连接对象的获取</h2>
<p><code>为了方便看代码，我不去捕获，直接将SQL异常抛出。</code></p>
<pre><code class="language-java">public class C3P0Demo{
    public static void main(String[] args){
        DataSource ds = new ComboPooledDataSource();
        Connection conn = null;
        for(int i = 0;i &lt; 20;i++){
            System.out.println(ds.getConnection());
        }
    }
}
</code></pre>
<h2 id="四-进行一些crud操作">四、进行一些CRUD操作</h2>
<pre><code class="language-java">public class C3P0Demo{
    public static void main(String[] args){
        DataSource ds = new ComboPooledDataSource();
        Connection conn = ds.getConnection();
        String sql = &quot;select * from user&quot;;
        PreparedStatement pstat = conn.prepareStatement();
        ResultSet rs = pstat.executeQuery();
        while(rs.next()){
            System.out.println(rs.getInt(&quot;id&quot;)+&quot;\t&quot;+rs.getString(&quot;name&quot;)+&quot;\t&quot;+rs.getInt(&quot;age&quot;)+&quot;\t&quot;+rs.getString(&quot;gender&quot;)+&quot;\t&quot;);
        }
    }
}
</code></pre>
<blockquote>
<p>原文作者：絷缘<br>
作者邮箱：zhiyuanworkemail@163.com<br>
原文地址：<a href="https://zhiyuandnc.github.io/c3p0/">https://zhiyuandnc.github.io/c3p0/</a><br>
版权声明：本文为博主原创文章，转载请注明原文链接作者信息</p>
</blockquote>

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